It is an important aspect of articles to be used outdoors or in wet or damp environments that they be impervious to water and moisture. Traditionally this has required that such articles be entirely coated with a waterproof compound such as rubber that renders then non-breathable, and therefore, uncomfortable when worn or used in close proximity to the body. One Example of such an article of footwear coated with rubber to make it waterproof is found in U.S. Pat. No. 1,972,976 to Burnham et al. Despite that this construction prevents outside water and moisture from entering the footwear, the rubber coating maintains all moisture, including perspiration, within the footwear, making the article very uncomfortable for prolonged wear. Thus, a material suitable for use in a wet environment and capable of moving perspiration away from the body was necessary.
To this end, various materials have been developed that are waterproof, but are also water vapor permeable. One example is the material available under the trademark GORE-TEX.RTM. available from W. L. Gore & Associates, Inc. of Newark, Del. Another example of a waterproof, breathable fabric is sold under the name NEPTUNE.TM. by Tempo/Shain Corporation of Peabody, Mass. Both of these materials utilize a porous membrane that has a pore diameter small enough to prevent water molecules from passing through, but large enough to permit water vapor molecules from passing through.
A problem with the use of these membrane materials in constructing waterproof articles of manufacture, be it footwear, apparel, camping gear, etc., is the water leakage that occurs along seams used to join various pieces of the material together to form the article. One solution to this problem is found in U.S. Pat. No. 4,599,810 to Sacre (assigned to W. L. Gore & Associates, Inc.). The Sacre patent describes a liner for footwear including a waterproof seam construction in which a tape comprising a nylon layer, a GORE-TEX.RTM. membrane layer, and an adhesive layer is laminated to the seams forming the liner. While this structure has proven successful in preventing water penetration, it is a very labor intensive process, requiring the collation of many parts by skilled workers. Therefore, is not wholly reliable and is not ideally suited for mass production.
Another example of a technique for waterproofing seams of footwear is found in U.S. Pat. No. 3,035,291 to Bingham, Jr. The Bingham patent discloses, in FIG. 3, a waterproof seam construction similar to the Sacre patent in that the seams are covered with a plastic adhesive coated tape. In the alternative, as shown in FIG. 5 of the Bingham, Jr. patent, a ply of gum rubber or suitable synthetic plastic may be interposed between plies of material adjacent the seams to seal the same. While this patent discloses waterproof seams structures, it too suffers from the problems associated with the Sacre patent in that the processes are very labor intensive and therefore, expensive.
U.S. Pat. No. 4,901,450 to Chemello (assigned to Salomon S. A. Annecy of Cedex, France) discloses an inner boot made of open cell foam for a ski boot. A lower portion of the inner boot is coated with polyurethane that seals against moisture and humidity. While the patent explains that the disclosure may be applied to inner boots of the stitched or sewn type, it does not provide for the coating to be selectively applied, for example, only adjacent the stitching or sewing. Thus, if applied to an inner boot made of breathable fabric, the breathability of the entire lower portion of the boot would be lost. Such a construction is unacceptable to today's consumer who wants an article to be waterproof, but does not want to sacrifice comfort by giving up breathability.
Thus, the need exists for a waterproof article of manufacture that is both waterproof and breathable, that avoids the problem of water penetration adjacent seams by providing a simple and cost effective seal. It is with this in mind that the present invention was developed. The present invention reduces the number of manual operations necessary in current waterproofing methods, and therefore, is more cost effective and reliable.